In order to support PCI resource mapping as described above, Linux platform-code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.-Platforms are free to only support subsets of the mmap functionality, but-useful return codes should be provided.+code should ideally define ARCH_GENERIC_PCI_MMAP_RESOURCE and use the generic+implementation of that functionality. To support the historical interface of+mmap() through files in /proc/bus/pci, platforms may also set HAVE_PCI_MMAP.++Alternatively, platforms which set HAVE_PCI_MMAP may provide their own+implementation of pci_mmap_page_range() instead of defining+ARCH_GENERIC_PCI_MMAP_RESOURCE.